Topic: Remote Battery

[SnowHiker]

Well then I need to use a Battery Eliminator to do a remote battery pack LOL...all this talk of using the DC jack on the board doesn't do what I want - it would override the solar panel and the cap.

It seems so.  If you used the jack on the board, when a power outage occurred it appears the supercap would drain quickly, not providing adequate backup for prolonged outages, even if it doesn't completely override the panel and cap.

Otherwise it seems if the jack was used under normal operation the station would continually be running on house current from the adapter, basically bypassing the panel and cap.

So yes, it appears your original idea was best for what you are asking.

[dalecoy]

Then when you want to quickly discharge the supercap, why do you plug in the unpowered adapter to it if it doesn't affect it?

I don't.

Have you actually done that, and checked the results?  It doesn't work (at least on recent models).

And what is the specified maximum voltage rating of the supercap?  [Hint: it's a lot less than the 5V output of the adapter]

[SnowHiker]

I don't.

That doesn't surprise me as I thought you had a cabled station.

Have you actually done that, and checked the results?  It doesn't work (at least on recent models).

How do you know it doesn't work?  Yes, I have tried it along with the flashing LED, TBH I don't know how fast it would have discharged otherwise, but it seems to be commonly thought on this forum that it does discharge the cap much faster, but we could be wrong.  And I do have an older model.

And what is the specified maximum voltage rating of the supercap?  [Hint: it's a lot less than the 5V output of the adapter]

I've checked my solar panel in bright sunlight and it was putting out around 2.5V. Are you saying that the higher voltage can't override the lower voltage?

N.B. - the #6625 AC-adapter INPUTS AC-voltage but OUTPUTS 5VDC voltage which over-rides the 3VDC from the CR123A battery...and...the Super Cap voltage.

[dalecoy]

The station that I operate continuously is a cabled station, yes.  That doesn't mean I have no information about wireless stations.

Davis uses protective diodes in all power circuits.  The (recent, at least) ISS is no exception.

No, I am not saying "higher voltage can't override lower voltage" - but please define "override".

And I don't know what Old Tele man means by "overrides". 

Davis circuitry (based on diodes to prevent reverse-flow) allows the highest available voltage source to power the ISS.  That just makes sense.  They also protect the supercap from reasonable over-voltage conditions.

Having said that, yes, soldering wires to the battery holder will work - it's just more convenient to use the jack that Davis provided.  [And the on-board battery could be left in, to provide an additional power source]

[dalecoy]

Yes, I have tried it along with the flashing LED, TBH I don't know how fast it would have discharged otherwise, but it seems to be commonly thought on this forum that it does discharge the cap much faster, but we could be wrong.  And I do have an older model.

Let's hear from someone who has (without using the "flashing LED" also) used the power adapter to try to discharge the supercap, and then actually measured the voltage on the supercap. 

[SnowHiker]

The station that I operate continuously is a cabled station, yes.  That doesn't mean I have no information about wireless stations.

Davis uses protective diodes in all power circuits.  The (recent, at least) ISS is no exception.

No, I am not saying "higher voltage can't override lower voltage" - but please define "override".

And I don't know what Old Tele man means by "overrides". 

Davis circuitry (based on diodes to prevent reverse-flow) allows the highest available voltage source to power the ISS.  That just makes sense.  They also protect the supercap from reasonable over-voltage conditions.

Having said that, yes, soldering wires to the battery holder will work - it's just more convenient to use the jack that Davis provided.  [And the on-board battery could be left in, to provide an additional power source]

Given all that, I'm not sure what the purpose of your "hint" in your previous post was.  I think it's pretty clear that by "override" it was meant that the power from the adapter would be used instead of the power from the solar cell/supercap.  (Please don't ask me what "used" mean now.  )

Does the circuit protection circuitry also protect the supercap from discharge when connected to a coil with a certain amount of internal impedance (such as an ac/dc adapter)?

As I mentioned before, yes he can leave the battery in the ISS, where it should last for years, whether or not the solar charging system still works with the adapter connected, assuming no frequent or prolonged power outages.  But the whole purpose of his endeavor was to remove the battery from the ISS in the first place where he could easily replace it when needed.  I've never had any experience with a lithium battery leaking or corroding, but I would still be wary about leaving it where I couldn't at least check it periodically.  But that may just be me.

It may be slightlly more convenient to use the jack, but simply connecting wires to the ISS from an external battery holder would be a one time thing, and he would most likely need to extend the adapter, which itself would involve splicing.  And before he uses the jack I would think he would want to know for sure that the ISS would keep transmitting in a power outage.

It sounds to me that the OP just wants to do what he asked about in the first place, but if he is interested in following the other suggestions, he would probably be well advised to do a little experimenting on his own while he has the station down and easily accessible.

As someone mentioned, a cabled station may have been better, assuming extra sensors, or the ability to move the console wasn't desired. So even if the battery is remoted, the wireless is still more flexible.  But, while looking at all possibilities is good, I'm not really seeing what the big problem is with the OP's original idea.

[Mattk]

Well then I need to use a Battery Eliminator to do a remote battery pack LOL...all this talk of using the DC jack on the board doesn't do what I want - it would override the solar panel and the cap.

So what is it you exactly want? and why won't the DC jack do it.

As previously mentioned power the DC jack with a 6V or 12v/5v DC convertor from battery/charger and totally forget about the Supercap and solar panel. The CR123 battery can then be optional

[SnowHiker]

A couple of other ideas not discussed yet:

-Put a huge street lamp in front of it that comes on at night to shine on the solar cell and keep the supercap charged even on the longest, darkest nights, so that a battery should never be needed.  Maybe add a generator if you're worried about a power outage that happens to last all night.

-Install it permanently on your vehicle and power it by your truck/car battery.

(This post may be two days early.)

[dalecoy]

Does the circuit protection circuitry also protect the supercap from discharge when connected to a coil with a certain amount of internal impedance (such as an ac/dc adapter)?

Yes.  [I presume you're asking about the circuitry between the external power jack and the supercap, etc.]

[And also, assuming that the recently-manufactured adapters are constructed that way, would be incorrect]

[SnowHiker]

Yes.  [I presume you're asking about the circuitry between the external power jack and the supercap, etc.]

[And also, assuming that the recently-manufactured adapters are constructed that way, would be incorrect]

How do you know all this, and how are recently-manufactured adapters different than the ones that have come before?

[SnowHiker]

Also, can I assume that since Davis much improved the power circuitry and isolated the various components so effectively, that bad capacitor, particularly one that fails in the shorted mode, will no longer cause the battery to drain prematurely?

[dalecoy]

Also, can I assume that since Davis much improved the power circuitry and isolated the various components so effectively, that bad capacitor, particularly one that fails in the shorted mode, will no longer cause the battery to drain prematurely?

You can't assume that - because a capacitor that fails doesn't "cause the battery to drain prematurely".  A failed capacitor doesn't store energy, and therefore the battery has to power the ISS.  That is, of course, the job of the battery - to power the ISS when there are no other available power sources.

(Rough explanation): If the capacitor fails "open circuit", the solar cell powers the ISS during the day, and the battery powers it at night, thus draining the battery.  If the capacitor fails "shorted", that effectively shorts out the solar cell, and therefore the battery powers the ISS full-time.  Thus draining the battery faster. 

The job of the battery is to power the ISS in the event that the other power sources fail. 

[dalecoy]

Yes.  [I presume you're asking about the circuitry between the external power jack and the supercap, etc.]

[And also, assuming that the recently-manufactured adapters are constructed that way, would be incorrect]

How do you know all this, and how are recently-manufactured adapters different than the ones that have come before?

1.  Davis isn't dumb, and that sort of simple diode-isolation circuitry is taught in Electrical Engineering 101 class.
2.  I have examined a fair amount of Davis circuitry.

Early adapters were simple transformer circuits, which were inefficient, and (probably of most importance to Davis) costly to manufacture, primarily because of the large amount of copper required.

More recent power adapters use an active circuitry which is much more efficient, and costs a lot less.  It also generates electrical "noise" on the DC output, therefore requiring a ferrite isolator on the DC line (that big fat thing on the wire).

johnd could tell us approx. when that change was made - and maybe if the part number actually changed.

[SnowHiker]

You can't assume that - because a capacitor that fails doesn't "cause the battery to drain prematurely".  A failed capacitor doesn't store energy, and therefore the battery has to power the ISS.  That is, of course, the job of the battery - to power the ISS when there are no other available power sources.

(Rough explanation): If the capacitor fails "open circuit", the solar cell powers the ISS during the day, and the battery powers it at night, thus draining the battery.  If the capacitor fails "shorted", that effectively shorts out the solar cell, and therefore the battery powers the ISS full-time.  Thus draining the battery faster. 

The job of the battery is to power the ISS in the event that the other power sources fail.

Nah, there are plenty of examples of batteries dying within weeks or less when a supercap fails, not the eight months or so that Davis claims. Read over these forums, you should find many examples, and I know from personal experience how quickly a battery can drain, even after fresh ones are put in when a cap fails. On one board which this happens I unsoldered the cap and the battery lasted for a good long time.  I also have a temp station without a cap and can verify that the battery lasts for many months.

So you really don't need to talk to me, or many others who have experienced supercap failures, how the battery is supposed to work.

[dalecoy]

Nah, there are plenty of examples of batteries dying within weeks or less when a supercap fails, not the eight months or so that Davis claims. Read over these forums, you should find many examples, and I know from personal experience how quickly a battery can drain, even after fresh ones are put in when a cap fails. On one board which this happens I unsoldered the cap and the battery lasted for a good long time.  I also have a temp station without a cap and can verify that the battery lasts for many months.

So you really don't need to talk to me, or many others who have experienced supercap failures, how the battery is supposed to work.

Oh - you meant premature as in days or a few weeks.

Those rapid battery failures are primarily the result of a capacitor that failed, and leaked conductive electrolyte onto the circuit board.  That effectively bypasses the Davis circuitry and causes a lot of drain on the battery.

I'm guessing that when you unsoldered that capacitor, you also cleaned up the messy electrolyte. 

(And no, I really don't need to talk to you)

[SnowHiker]

1.  Davis isn't dumb, and that sort of simple diode-isolation circuitry is taught in Electrical Engineering 101 class.
2.  I have examined a fair amount of Davis circuitry.

Early adapters were simple transformer circuits, which were inefficient, and (probably of most importance to Davis) costly to manufacture, primarily because of the large amount of copper required.

More recent power adapters use an active circuitry which is much more efficient, and costs a lot less.  It also generates electrical "noise" on the DC output, therefore requiring a ferrite isolator on the DC line (that big fat thing on the wire).

johnd could tell us approx. when that change was made - and maybe if the part number actually changed.

I'm glad we live in a perfect world where electronics theory and real world applications all work perfectly.

So can you verify for me that when the new (switching?) adapters are unplugged that the resistance between the pos and neg contacts of the connectors are infinite?

I'm also curious if the adapter jack on the wireless system was really meant to be an alternate power source, or is just there for testing, or just because they just put more or less the same components on the wireless and cabled boards.  For example, my extra temperature station for the VP1 wasn't even meant to be solar powered, it was an indoor station, yet it still had the very same board as the ISS including the supercap.

The point is, do you know exactly how the jack interfaces with the solar charging circuitry, or are you making assumptions yourself?

[dalecoy]

So can you verify for me that when the new (switching?) adapters are unplugged that the resistance between the pos and neg contacts of the connectors are infinite?

No, it is not infinite.  That's not the way diode protection works.

I'm also curious if the adapter jack on the wireless system was really meant to be an alternate power source, or is just there for testing, or just because they just put more or less the same components on the wireless and cabled boards. 

Yes, No, Sorta.

Perhaps johnd will comment.

[SnowHiker]

For example, my extra temperature station for the VP1 wasn't even meant to be solar powered, it was an indoor station, yet it still had the very same board as the ISS including the supercap.

BTW, you may consider just consider this anecdotal evidence, but when a cap died in my ISS, I removed it and swapped the board with the temp station as it didn't need a supercap.  The battery seems to last much longer in the temp station since I put the board in without a cap, even though the cap was good.  I can't give hard evidence as I use the temp station for a few months in winter, and I started putting in the used battery from the ISS when I swap it out for a new one every couple of years.  But even used the battery seems to have more than the eight month life Davis claims, and seems to last longer than a fresh battery did in the temp station with the good cap.  So that helps convince me that the components aren't perfectly isolated and have no effect on each other.

[johnd]

Perhaps johnd will comment.

Sorry, don't really have anything useful to add - I suspect that only those in the original Davis design team know the answer. Maybe it's for testing (though that would maybe imply manual testing, which would be somewhat clunky).

Or perhaps it was totally minimal cost to add a belt and braces aspect with the extra 5v input or simply to provide more flexibility to the powering options. It's maybe not unrelated that the AC-powered repeater versions (7626/7653) have been discontinued as unnecessary given that the solar-powered version can be AC-powered anyway.

TBH I'm not sure there's much point in speculating - AFAIK no-one outside of Davis knows the precise circuit-level details of eg how the power options (solar/supercap/battery/5v) are designed or how they might have changed over time and so we're unlikely ever to find out whether any given theory is right or wrong.

[dalecoy]

Thanks, johnd

You did mention the differences in adapters in this previous note: 
http://www.wxforum.net/index.php?topic=13958.msg136450#msg136450

And my statements are based on examination (and some tests) of a wireless circuit board (with a supercap problem) that I repaired for a friend.  As well as the fact that the diode protection (which you mentioned in that note) is standard engineering practice.

But, as you also noted - many things may have changed over time.

There might have been a version that viewed that jack as (also) a possible way to supply power to some external device, which would explain the (then) lack of diode protection, and the (then) ability to discharge the supercap using that jack.

[azchrisf]

I'd be curious -

Can anyone who knows the internals throw up a quick schematic of how the power handling in an ISS works?

[dalecoy]

I'd be curious -

Can anyone who knows the internals throw up a quick schematic of how the power handling in an ISS works?

That would be useful.  I have measured some of those characteristics (on only one sample), but not enough to draw a schematic.  "Hacking" a schematic would require destructive analysis of a circuit board.  And there might have been design changes over the years. 

For instance, I measured that the external power jack can provide power to operate the ISS, but the battery in the ISS does not provide power output through that external power jack.  But I didn't measure a lot of other things - for instance, I don't know if the external power jack can be used to charge the supercap.  Nor whether the solar panel can provide power output through that jack.  Etc. 

Disregarding the external power jack, we know that (depending on available voltage):
1.  The solar panel can power the ISS and charge the supercap.
2.  The supercap can power the ISS.
3.  The battery can power the ISS, but does not charge the supercap.

From there, several different schematics could be drawn.  I would be happy to see an official schematic, of course.

[adnadeau]

I know this is an old post; I just ran across it.  Here's a couple of pictures of the SIM PCB, both to the same scale.  You can see that the power distribution is complicated.  Looking at the reversed PCB back picture, notice the 3 large through-holes in a triangle configuration.  The right one goes to the center contact of the power jack, the left one to the shell, & the bottom one is a N.C. to the shell (my assumption based on a datasheet of a similar jack).  The thick trace goes to the supercap neg through-hole.  On the top of the PCB, the center pin contact goes to a cylindrical surface mounted diode D12 & then to D11 & then ??  The solar panel pins go somewhere else.
 [ You are not allowed to view attachments ]  [ You are not allowed to view attachments ]

[dalecoy]

Thanks for the additional information. 

[rdsman]

Here is some food for thought about the power circuitry:

I have a Vue ISS.  About one year ago I got the dreaded "Low Battery" message.  I replaced the battery with a good one but was unable to clear the message on the console.  I took the new battery out and measured the voltage and it was now dead.  I connected my bench power supply to the ISS battery terminals and it maxed out the current limiter in the power supply.  So I measured the battery input of the ISS with an ohmmeter - it is .1 ohms forward and reverse.  It is not going to work that way.

The ISS at that time would still run on solar power and charge the supercap.  A month ago it stopped charging the supercap.  Now it will only run on solar power as long as the sun is shining.  Or it will run off of my bench power supply in place of the solar cell.

Time for something new!